Sorry for the very late reply, thank you to everyone who has given me advice thus far. I will try and address all points in this post whilst giving an update.
I met with my supervisors again and they basically told me that in no uncertain terms will they ever give me a reccomendation to work in any laboratory environment whether industrial or academic. They do not think I should ever do a post-doc and that my lab skills are not up to par.
I then scheduled another meeting with a mediator and they changed their tune very quickly. The tone was more "we advise you look for jobs better suited to your abilities such as writing roles or management roles." They denied a lot of things they said and afterwards I spoke with the mediator who mentioned that they had a very good feeling they were lying to them.
I have a job now and a viva date set for the end of April. I have gone to my students union and put in a complaint about my supervisors and that is currently being investigated. A post-doc in my lab looked at the references that my supervisors had given me, and they were shocked at the level of bias. The post-doc has said that they will do my references for me because "its clear prof x and dr y have had it in for you for a while now." We had a frank discussion of my abilities and the post doc said "If I was grading you out of 10 like prof x and dr y had, I would have given you 7 for professional conduct, 7 for interpersonal, 10 for honesty 10 for timekeeping, 7 for time management. Your quality of work and productivity I would have scored you average, you weren't the best but you tried hard and worked hard when it counted." They were shocked I was given 1/10 or 2/10 in every category. I spoke with ex-lab members who also saw the references and said that it showed clear bias and they would be willing to write character references to the university of the investigation. The industrial sponsor has not seen the references because I do not want to cause that fight, but they have written more accurate references for me and told me to go to them for references as "academics rarely know what to write in these things and its easy for them to slip up and cost you a job." I dont know what they mean by that exactly...
To give a bit more detail. My supervisors and I have been at loggerheads for 3.5 of the 4 years of the PhD and I have had to fight them on every decision, every route change, every piece of work, at literally everything. In year 1 the industrial sponsor wanted a piece of work done and gave my supervisors the go ahead to do what was needed. After 3 months, nothing was working so I wrote up my results, did a literature report with it, and argued for a route change showing that the work we were doing was not ever going to work. My supervisors said "no" and told me to go away and "make it work." I argued that the fundamental chemistry would not work and showed them paper after paper to back up my claim. It was dismissed. I went to the industrial sponsor and pleaded my case, an emergency meeting was called, threats to pull funding were made, I was allowed to do my route change... 2 years later.
In that intervening two years the following happened. I was tasked with making a library of compounds. After 4 were made, I was told they would be sent for testing and NOT to complete the library until the results were in. The industrial sponsor did not like this and told me finish the library. It took that two years to do it because of... My supervisors fighting with me and the industrial sponors. In the meantime I was working on route 3 and that wasnt going well but I made it work with no real interference from my supervisors or my industrial sponsor. They were pleased with that at least.
Whilst doing route 3, the compounds that were sent for testing were not tested because the company went under and it took 2 years to find another place to do it, the contracts are not sorted yet and I have already submitted my thesis so I cant benefit from the results. I finished the first library in 2015 two years after I started it and I started the route change I argued for in 2015 also. So it took two years to get to where I should have been by 2014.
To answer Iranur, when I said I spent most of my time doing reactions I knew would not work, I meant exactly that. My supervisors never listened to my concerns about certain routes and would send me away to do "more research" either literature or experimental to prove nothing was working. I wasted so much time on reactions that would never have worked but my supervisors insisted that I do them anyway for "completeness." I spent months arguing for route changes, different reagents, conditions etc to be used and they resisted until I went to the industrial sponsor or just went behind their back and ordered the chemicals I wanted after I got them to sign an order form. I would add the chemicals I wanted after the fact.
The post doc thinks that this is why they have given me bad references and said I had bad interpersonal skills, because I would always go around them and get what I wanted. They hated not having full control of the project and hated that I would go to the industrial sponsor and put pressure on them to do things. In the end, I made my own bed by just doing what I thought was right for the project. I should have just did what my supervisors said and let the PhD fail because its what would have happened if I did not fight for every inch to do what was necassary. I even had to go to the university to get time to write my thesis. They wanted me to write the whole thing in the month before submission because they wanted me in the lab until the day I submitted. I complained that no one else in my lab had to do that and most people were given 3 - 6 months to write up. I started writing at the start of my final year and I did not get back drafts until 8 months later because "we dont want you writing yet."
I am so glad that in 1 month I NEVER have to deal with them again.